This invention relates to a rocker-type such as a single pole double throw switch, and more particularly to an improved construction for a contact carrier and an actuating plunger for use in such a switch.
A rocker-type switch, such as a single pole double throw (SPDT) switch, typically includes a housing within which first and second stationary contacts are mounted, and a stationary center contact is located between the stationary first and second contacts. In the prior art, the center contact has a channel shape. A V-shaped movable contact member or rocker is, formed of an electrically conductive material, is engaged with the channel-shaped center contact, and selectively connects the center contact to either the first stationary contact or the second stationary contact, in response to operation of an actuator movably mounted to the housing. Each leg of the V-shaped movable contact member carries a button-type contact that establishes contact with the underlying first or second stationary contact. The actuator is pivotably mounted to the housing, and includes an extendible and retractable plunger in engagement with the movable contact member. When the actuator is in an OFF position, the plunger is engaged within the trough or valley defined by the apex of the V-shaped contact member, which positions the V-shaped contact member such that the button-type contacts are out of contact with the first and second stationary contacts. Movement of the actuator to an ON position functions to move the plunger away from the trough or valley defined by the apex of the V-shaped contact member, along one of the legs of the V-shaped contact member to cause the movable contact member to rock or pivot on one of the walls of the channel-shaped stationary center contact. Such movement of the plunger functions to force the leg of the contact member downwardly, to bring the button-type contact into engagement with its associated underlying stationary contact. When the actuator is returned to its OFF position, the plunger is returned to the trough or valley defined by the apex of the V-shaped contact member, to rock or pivot the V-shaped contact member on the wall of the center contact and to raise the button-type contact out of engagement with its associated stationary contact. In the prior art, the distal end of the plunger is generally spherical in shape, which enables the plunger to move smoothly along the legs of the movable center contact member as the actuator is moved between its ON and OFF positions. However, the spherical shape of the plunger outer end does not match the geometry of the center contact member. This creates a problem when the actuator is in its OFF position, in that the xe2x80x9crest positionxe2x80x9d, i.e. the position of the movable center contact member when the actuator is in its OFF position, is indeterminate. That is, the position of the movable center contact member can vary throughout a range of positions when the actuator is in its OFF position, due to the fact that the spherical end of the plunger has a configuration which does not match the configuration of the sharply angled apex defined by the legs of the center contact member. The resultant uncertainty in the position of the center member when the actuator is in its OFF position is undesirable in that the parting distance of the movable contact members from the stationary contact members is unknown and can vary widely from one actuation to another.
It is an object of the present invention to provide a plunger-actuated switch, such as a rocker-type switch or the like, with an actuator arrangement that ensures consistency of the movable contact member when the actuator is in its OFF position. It is a further object of the invention to provide such a switch which is of similar construction to prior art switches, and entails a relatively minor modification in the construction of the plunger so as to reliably and consistently position the movable contact member when the actuator is in its OFF position. A still further object of the invention is to provide such a switch in which the plunger is configured to take advantage of the existing construction of the movable contact member, to facilitate movement of the movable contact member and positioning of the movable contact member when the actuator is in its OFF position.
In accordance with the invention, an electrical switch generally includes a housing including a base defining an internal cavity, in combination with a cover engageable with the base and an actuator movably mounted to the cover. A stationary center contact is secured to a lower wall defined by the base, and spaced apart stationary first and second contacts are secured to the lower wall of the base on opposite sides of the stationary center contact. The switch further includes a movable contact member defining a central portion in engagement with the stationary center contact, and a pair of spaced apart end contact areas. A movable actuator is interconnected with the housing, and interacts with the movable contact member to selectively establish contact with either the first or second spaced apart stationary contacts. The actuator is movable between an OFF position, in which the movable contact member is maintained out of engagement with both the first and second contacts, and one of two ON positions. In a first ON position, the actuator is operable to move one of the contacts of the movable contact member into engagement with the first stationary contact, to establish an electrical path between the first stationary contact and the center stationary contact. In the second ON position, the actuator is operable to engage the second contact of the movable contact member with the second stationary contact, to establish an electrical path between the center contact and the second stationary contact.
The stationary center contact defines an upwardly facing substantially planar contact surface, and the stationary first and second contacts also define upwardly facing substantially planar contact surfaces. The movable contact member has a nonlinear configuration, and may be in the form of a V-shaped member having first and second arms extending outwardly from a common center or apex. Each of the first and second arms has a contact member secured toward its outer end. The actuator includes a spring biased plunger which interacts with the movable contact member so as to provide movement of the movable contact member between its first and second ON positions. The plunger includes an outer end that engages the movable contact member, and the spring bias of the plunger functions to bias the outer end of the plunger into engagement with the movable contact member.
The outer end of the plunger has a configuration that matches the configuration of the movable contact member. The plunger, actuator and movable contact member are configured such that the matching configuration of the movable contact member and the end of the plunger are in a complementary, mating relationship when the actuator and the movable contact member are in the OFF position. The end of the plunger defines a pair of surfaces which correspond to the V-shaped configuration of the movable contact member, which engage the surfaces of the movable contact member defining the trough or valley defined by the apex of the movable contact member when the actuator and movable contact member are in the OFF position. This matching configuration of the plunger and the contact member functions to positively maintain the movable contact member in a position in which the contacts of the movable contact member are at an equal elevation relative to the associated underlying stationary contact. The end of the plunger defines a tip between the side surfaces, which remains in engagement with the movable contact member as the actuator is moved between its ON and OFF positions, to impart rocking or pivoting movement to the movable contact member on the center contact in response to movement of the actuator. The side surfaces of the outer end of the plunger cooperate with the configuration of the movable contact member so as to provide a xe2x80x9cself-rightingxe2x80x9d action as the actuator approaches its OFF position, to facilitate positioning of the actuator in its OFF position and to positively retain the movable contact member in a consistent and predictable OFF position, in which the contacts of the movable contact member are maintained at an equal and consistent elevation relative to the underlying stationary contact when the actuator and movable contact member are in the OFF position.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.